1. Field of the Invention
The present invention relates to a radiation-proof resin composition in which a salicylate-based UV absorber, a benzotriazole-based IN absorber, and a triazine-based UI absorber are added to a polyolefin-based resin, and radiation-proof wire/cable using the radiation-proof resin composition as a material of an insulator or sheath.
Priority is claimed on Japanese Patent Application No. 2007-239723, filed Sep. 14, 2007, the content of which is incorporated herein by reference.
2. Description of Related Art
Insulators and sheaths of wires and cables, resin pipes, and other resin products disposed in places where radiation exists, such as nuclear power plants, radioactive waste storage facilities, and research and medical facilities treating radioactive materials, are deteriorated due to exposure to the radiation and decrease in mechanical characteristics, thereby reaching dielectric breakdown.
For example, Japanese Patent No. 2608782 discloses a radiation-proof resin composition that is protected from radiation by adding a specific antioxidant and a salicylate-based UV absorber to a polyolefin-based resin as a resin composition for insulators and sheaths of wires and cables used in places exposed to the radiation.
For example, Japanese Unexamined Patent Publication No. 9-12786 discloses a radiation-proof resin composition that is protected from radiation by adding a specific antioxidant and a benzotriazole-based UV absorber to a polyolefin-based resin.
A benzotriazole-based UV absorber or a hindered amine-based light stabilizer is widely used to give light resistance to the polyolefin-based resin. For example, it is disclosed in the description on a specific hindered amine-based light stabilizer of “www.tenkazai.com, light-resistance stabilizer”, [online], (Ciba Specialty Chemicals Ltd., 2005, [searched on Nov. 9, 2005], Internet URL: http://tenkazai.com/ciba/syousai_taikou.html#a7—2) that a synergistic effect is obtained by combination of an antioxidant and a UV absorber.
However, when the polyolefin-based resin composition employing the mire disclosed in the Japanese Unexamined Patent Publication and the Japanese Patent was exposed to radiation with 1 MGy and then was subjected to a tension test, it could be confirmed that the elongation at break was more markedly deteriorated than before the exposure and it was difficult to pass a frame test of cable. On the other hand, when the amount of mixed additives is increased so as to improve the radiation-resistant properties, there is a problem with blooming (spout of powder) of the additives.
Light resistance can be expected from the resin composition obtained by adding the combination of the benzotriazole-based UV absorber and the hindered amine-based light stabilizer to the polyolefin-based resin. However, when the resin composition is exposed to radiation and is subjected to a combustion test, the flame retardant properties thereof are more markedly deteriorated than prior to the exposure. When the amount of mixed additives is increased so as to improve the radiation-resistant properties, there is also a problem with blooming (spout of powder) of the additives.
Therefore, the invention is contrived to solve the above-mentioned problems. An advantage of some aspects of the invention is to provide a radiation-resistant resin composition that is excellent in mechanical characteristics even after exposure to harsh radiation with 2.5 MGy, that exhibits a suitable radiation-resistant property by a small amount of mixed additives, and that can suppress the blooming of the additives, and a radiation-proof wire/cable using the radiation-resistant resin composition as a material of an insulator or sheath.